NASA is
watching closely as Russian engineers hunt for the source of a malfunction that
sent a returning Soyuz spacecraft off-course during a Saturday landing.

Bill
Gerstenmaier, NASA?s space operations chief, said Tuesday that it is too early
to speculate the root cause of glitch or even how much additional peril, if
any, the spacecraft?s three-astronaut crew was in, despite recent Russian
news reports.

?They?re
concerned about the event, but the relative danger to the crew, we?ve had no
discussion on that at all,? Gerstenmaier told reporters in a teleconference,
adding that he had not heard of any claims from Russian officials that the
crew?s lives were in danger. ?They?ve not conveyed to us or conveyed to me any
concerns at this point.?

The
Russian-built Soyuz TMA-11 spacecraft successfully returned
to Earth on Saturday from the International Space Station (ISS) with Expedition
16 commander Peggy Whitson, flight engineer Yuri Malenchenko and South Korean
astronaut So-yeon Yi aboard.

It returned
on a ballistic trajectory, a backup landing profile that sends the reentry
capsule back to Earth in an unguided spin, as well as on a steeper-than-normal
course that subjects the crew to up to eight times the force of gravity before
parachutes deploy. Nominal landings hit peak loads of at about six times the
force of gravity.

?It was
pretty, pretty dramatic,? said Whitson, who completed a six-month spaceflight
with Malenchenko, in a post-landing audio recording released late Tuesday. ?Gravity
is not really my friend right now and 8 Gs was especially not my friend.?

Off-target
touchdown

But
sometime during the descent, something went wrong. Instead of hitting its
target landing zone on the central Asian steppes of Kazakhstan, the spacecraft
landed short some 260 miles (420 km) to the east.

"There
was no action of the crew that led to this,'' Malenchenko in a post-landing
press conference on Monday, the Associated Press reported. "Time
will tell what went wrong.''

Malenchenko,
who commanded the Soyuz during launch and landing, contacted Mission Control
within an hour after landing - the earliest he could free himself from the
capsule - using a satellite phone to relay that he and his crewmates were home
and in good health.

Whitson
said local Kazakhs were first at the scene, possibly due to a fire nearby the
spacecraft. NASA officials said the fire was due to brush burning by nearby farmers
and unrelated to the Soyuz landing.

Malenchenko
and Whitson reported being shaken about in their seats early in the landing
operations, which suggests that the three-segment Soyuz spacecraft?s disposable
propulsion module may not have jettisoned as cleanly as designed, Gerstenmaier
said.

Another
potential culprit is an avionics cable that may have shortedout and
directed the Soyuz computers to initiate a ballistic descent, he added.

But Russian
and NASA engineers will have a better handle on the anomaly once the Soyuz crew
capsule and its flight recorder are retrieved.

?It may be
a month of so before we start hearing anything definitive back from the
commission,? Gerstenmaier said.

The
three-segment Soyuz spacecraft design has long been Russia?s workhorse of
manned spaceflight.

They consist
of a central 6,393-pound (2,900-kg) crew capsule sandwiched between an orbital
module on top and a propulsion module - which includes solar arrays and
propellant - on the bottom. The three modules separate during reentry, leaving
the bell-shaped crew capsule to return to Earth under parachutes and
retrorockets.

Gerstenmaier
said officials know the following:

Malenchenko and Whitson reported unusual buffeting,
jarring and shaking before entering the ballistic descent, suggesting the
propulsion module may not have detached properly.

The Soyuz spacecraft lost radio contact with Mission
Control during reentry for an as-yet unexplained reason. While some
Russian media reports suggest an antenna may have burnt away, there may
have been ground and air-based issues, Gerstenmaier added.

Malenchenko did report some signs of smoke inside the
Soyuz spacecraft during reentry and powered down a display panel at times.
Whether the smell came from inside the vehicle or through vents from the
exterior is undetermined.

A
short-circuit in a faulty cable prompted
the ballistic reentry of the space station?s Expedition 15 crew and a
Malaysian astronaut last October during a descent that also included a
propulsion module separation malfunction. The two glitches were thought to
be unrelated and the module later sheared away due to aerodynamic forces.

Reliable,
despite glitches

Saturday?s
ballistic reentry of a Russian Soyuz marked the second in a row and the third
since faulty gyroscope equipment forced the space station?s Expedition 6 crew
to make a
similar landingin May 2003.

?I don?t see
this as a major, major problem, but it is clearly something that should not
have occurred,? Gerstenmaier said. ?I think there is inherent reliability in
this system.?

They served
a pivotal role to continue ferrying astronauts to and from the ISS between 2003
and 2005 while NASA recovered from the tragic Columbia shuttle disaster. The
U.S. space agency is also banking on Soyuz vehicles to send NASA astronauts to
the ISS during the gap between the 2010 retirement of its space shuttles and
the first flights of their Orion capsule successor.

More Soyuz
spacecraft will also be needed beginning next year, when the space station?s
population is expected to jump from three astronauts to a full six-person
complement.

?We?ve been
discussing with the Russians their ability to support Soyuz production for next
year,? Gerstenmaier said. ?But again we need to watch and understand what the
failure mode was.?

After last
year?s ballistic return of the Expedition 15 crew, Russia?s Federal Space
Agency replaced the faulty cable on new Soyuz vehicles and double checked power
connections for the explosive bolts governing module separation.

But the
Soyuz TMA-11 spacecraft that launched Whitson and Malenchenko into space was
already docked at the space station by then. The astronauts safeguarded the
ballistic system cable using additional insulation, but could not check the
module separation system from inside.

The only
way to check that system in orbit would be in a spacewalk that would require
astronauts to don spacesuits, carefully peel back layers of their Soyuz
vehicle?s protective thermal blankets and examine connectors for each of the
explosive bolts, Gerstenmaier said.

?We
determined, along with the Russians, that that was probably more risky to go
out and pull those blankets back,? he added. ?We didn?t see any more fixes that
didn?t carry more risk associated with them than leaving it as it was.?

Gerstenmaier
said he expects NASA and Russian space officials to discuss any new findings
from the ongoing investigation prior the planned May flight of the Soyuz TMA-12
spacecraft currently docked at the space station. During that flight, NASA
astronaut Garrett Reisman and two Russian cosmonauts will move their Soyuz to a
new docking port.

?We really
need to get the capsule back to understand what occurred,? Gerstenmaier said.
?I don?t want us to speculate.?